Lawnboy gold series 10400, sn 4906038, failure to fire. Possible bad magneto. Looking for replacement part and magneto settings; i.e., gap between flywheel and the magneto. Any other tips appreciated.

I see anywhere from .030" (.76mm) - .035".. the smaller gap will be easier for the magneto to fire...and probably run better at low speeds..

Joe, Factory Lawn Boy SPARK PLUG 614009, replacement plugs champion CJ14, NGK plug # BMR4A.
Check the attached links,instruction and guides, Good luck
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Lawn Boy 10415 Lawn Boy Gold Series Walk Behind Mower 1995 SN 5900001...
614009 Spark Plug
Which spark plug for Lawnboy engine
https://www.shoplawnboy.com/Comergent/en/US/adirect/Toro?cmd=ToroLBOnlineModelLookup

check the magneto. temperatures can affect the spark production if you have a bad magneto coil.

If you are getting no fire it is going to either be your coil is grounding out through the kill wire somewhere or your coil has gone bad. Try unhooking your kill / ground wire directly from the coil then check for fire. If you still have no fire then you will need to replace the coil. Hope this helps.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/steve_f5a6ca85b5d1ffc9

This ignition design relies on proper setting of the points in relation to the magneto to produce a spark. It is possible that your aligning pin sheared causing the magneto to be out of place in relation to the points opening. Dirty points, improper gap, and a bad coil will all result in a 'no-spark' condition. Check out the attached video. It is not your bike, but the procedure is the same. How to Set Points

Hello John,
Is your spark weaker on 2nd cylinder? If thats the case I would replace the magneto. If spark is equal on both I would look at valves.I am willing to bet it is valves. I would check valves and adjust gap and try again. You could also set air gap of magneto also, but I think it is valves.

I’m happy to assist further over the phone at https://www.6ya.com/expert/layne_0fccff498c319c32

It all depends on the model of engine. If it is a twin engine doesn't it have two magnetos.Very unusual for both to go bad It will depend on the type of ignition(points or solid state) The wire going to the magneto could be the kill switch (kills when grounded) Disconnect it and see if you get spark. IF so then it is in your safety/ignition circuit. If you replace magneto usually the gap is .008-.012

most any newer tecumseh or briggs will be .012 air gap setting
lawnboy is.010 setting

Could be magneto bad, wire from magneto bad, ground on magneto bad, or the clearance between the flywheel and the magneto is rusted up if it was outside. Clean flywheel with sandpaper and set magneto gap using a match book flap.

Alright, remember that 2-Stroke motors are meant to do 2 things:
Break down, then Frustrate you.

So, here we go: (Electrical)

Rotor Magnets, Magneto (ignition coil), Spark Plug Wire, Spark Plug, Spark Plug Ground (Cylinder Head).

In that order!

Check your "fire" from the Magneto:

1. Check your Kill Switch. In other words, leave everything normal, and unhook it. Did she start? Kill Switch it is! Kill Switch/Wire comes from the Magneto (single wire/ground) to the Switch itself. So check that wire AT the Magneto (Is it loose and grounding out? Is the Kill Switch grounding you out where it is, because of crud, junk, or because it is touching the block when it is not supposed to?)

2. Check your Spark Plug Wire. Easy, unook it from the plug, stick your finger in, give it a crank (non-MultiMeter way). Did you get shocked? Then it ain't your Plug Wire and Magneto!

With a Multi-/Volt Meter, simply hook her up, and check for juice WHEN you pull the rope. If you got juice, it ain't your Plug Wire or Magneto!

Checking Spark the "normal" way: Grab the Plug with a pair of insulated pliers, hold the plug end against the cylinder head, and pull your rope. Any Spark? What color?

3. STILL no fire. It leaves: Magneto and Plug Wire.
Luckily, they are both in the same place! Tear your blower down, and check to see if the Magneto has slipped out of place (gap is WAY out), or if the Plug Wire has worn to the point it is grounding you out. While you are there, check your Kill Switch wire, to see if she is grounding you out then and there.

4. STILL no fire. That means: Magneto Failing, or Magneto JUNK.
Buy another one, replace it! (Or steal one from another junk Blower/Weedeater. These things are fairly standard, and easy!)
Or, Bad Plug Wire. Meaning she has failed out on you.
Wait......that means: Replace your Magneto! Lucky the things are built together right?